Treatment of latex and the extraction of india-rubber therefrom.



obtained from rubber trees SAMUEL GLELAND DAVIDSON, OF BELFAST, IRELAND.

TREATMENT OF LA EX AND THE EXTRACTION or IN A-RUBBER THEREFRQM.

No Drawing.

To all whom it may concern Be 'it known that I, SAMUEL CLELAND DAVIDSON,of Sirocco Engineering )Vorks, Belfast, Ireland, merchant, have inventedcertain new and useful Improvements in the Treatment of Latex and theExtraction of India-Rubber Therefrom, of which the following is aspecification.

My invention relates to the extraction or coagulation of india-rubberfrom the latex and more particularly from the variety known as Para or Hever: Brasz'lz'ensz's.

According to the methods hitherto ordinarily employed, for theextraction and coagulation of rubber from the latex, a free acid insuitable quantity is added thereto as a single treatment, or the latexis subjected to the action of smoke, and, by elther of these methods,coagulation of the rubber is accomplished, but simultaneously therewiththe resinous, protein, gummy and oily constituents of the latex(hereinafter referred to as impurities) also coagulate and become aconcomitant part of the rubber. These impurities have subsequently to beremoved so far as it is practicable to do so, before the rubber issuitable for employment in the impurities have become a component partof the rubber, their removal is not only very difficult, but frequentlyvery imperfectly effected, and is usually accomplished by passing'itthrough rollers rotating at different speeds with Water trickling overthem, which operation has a disintegrating, scrubbing and washing effecton the rubber. The machines used for this purpose are generally known asrubber washing machines. F urthermore, in the manufacture of vulcanizedrubber goods, it is a necessary part of the vulcanization processthatthe raw rubber be evenly impregnated with sulfur-throughout itsmass, and manufacturers usually accomplish this by first getting the rawrubber, when sufliciently purified, into a dough-like consistency bykneading it in special machines for the purpose, and gradually mix ingthe sulfur into it (generally in the form of flowers of sulfur).

Now the object of this invention among other things is to obtainsimultaneously with the coagulation of the rubber from the latex, itsthorough permeation with nascent precipitated sulfur, the chemicalactivity of which is known to be abnormal at the mo Specification ofLetters Patent.

Patented July 6, 1915.

Application filed November 9, 1912. Serial N 0. 730,352.

ment of its liberation from a. solution of the compound in which itpreviously existed,

. and also at the same time to restrain and to a considerable extentprevent the impurities hereinbefore referred to from coagulating alongwith and thereby becoming a. concomitant part of the coagulated rubber.My

, invention is applicable to said latex while it is in the fluidcondition in Which it is collected from the rubber trees, and whether ornot it has been subjected to previous treatment, such for example, aswhen ammonia .or other alkali or alkaline substance is added to thelatex during or soon after its collection from the rubber trees toprevent a tendency which sometimes exists to spontaneous coagulationbefore the latex can be brought into the factory, or when the latex inorder to preserve and retain it in a fluid condition is treated withformaldehyde or other suitsulfur salt (such as a polysulfid orthiosulfate of an alkali) from which sulfur may be precipitated by afeeble acid and subsequently add to the latex a suitable acid or acids,or other reagent, having a decomposing action on said soluble salt ofsulfur whereby simultaneously with the coagulation of the rubber, thesoluble sulfur salt will be decomposed, and nascent sulfur liberated inthe latex, which nascent sulfur will evenly impregnate. the rubberthroughout its mass.

The amount of the soluble salt of sulfur to be added to the latex,cannot accurately be defined by Weight or measurement, owing to thefactthat latex from diflerent localities often varies in itsproperties,and even.

latex from the same trees varies at different seasons, and morning andevening tappings also frequently vary in characteristics, andconsequently involve variations in the treatment, but I tained with anaddition to the fluid latex of an aqueous solution containing relativelyto the latex about 5 per cent. of the thiosulfate of soda, or about 3,per cent. of the'polysulfid of potash, or about 4 per cent. of anadmixture thereof in equal parts.

find that good results are ob-,

' end I first treat the fluid latex with a soluble fur salt be usedalone any acidity of the latex should be previously neutralized byaddition of alkali; In some cases I may also introduce or mix with theaqueous solution of the salt of sulfur a small quantity of formaldehyde,or other suitable disinfectant, such as an alkaline solution ofcreosote, or

oarbolic acid which, while in an alkaline condition and thus employed,have no coagulating effect on the latex, or I may .use mixtures offormaldehyde and such other disinfectant. v

According to a second modification of my invention, as applied to saidfirst treatment of the latex, I first render the soluble salt or saltsof sulfur employed distinctly alkaline by adding to same a suitableamount of alkali, or alkaline salt, or alkaline substance, such, forexample, as ammonia, soda, potash, carbonate of .soda, biborate of soda(borax), or an alkaline preparation of creosote, or of carbolic acid, orof an admixture of creosote and carbolic (hereinafter referred to asalkalized creosote, or alkalized carbolic, or alkalized creo-carbolic),which substances may be prepared by gradually mixing a strong lye ofsoda or potash into the creosote, or the carbolic acid, or thecreo-carbolic, until the mixture attains a syrupy condition, or saidalkalized creosote, or carbolic or creo-carbolic may also be prepared bygrinding together about four parts of borax with one part of creosote,or of carbollc, or of creo-carbolic, as the case may be, the resultingcompound in each case being in the form of a slightly damp powder having an alkaline reaction and which can be dissolved in water.

The above described preparations of alkal zed cresote, or alkalizedcarbolic, or alkahzed crcocarbolic, may then be mixed or ground in withthe sulfur salt employed in a ratio of one part of the former to aboutthree (or more or less) parts of the latter,

whereby an alkaline compound is formed,

witlrwhich I then prepare a dilute aqueous solut on for the firsttreatment of the latex by dissolving said alkaline compound in the ratioof one part of same to about 25 to 50 parts of water, and a sufficientquantity of this aqueous solution is then added to the fluid latex torender it faintly alkaline to test paper. )Vhen the latex has beensubected to said first treatment, in accordance with either of myhereinbefore described first or second modifications therefor, it isdesirable to keep the latex in this condition a sufficient time toinsure the required action of said first treatment on the latex, towhich end the dilute aqueous solution of the salt of sulfur employedmay, in some cases, be heated to any desired temperature up to boilingpoint, and while hot added to the latex, or the latex itself or both thelatex and the solution of sulfur salt may be heated. I now apply thesecond, or coagulating, treatment by adding and mixing into the latex adilute aqueous solution of any suitable acid or admixture of acids,which has or have a decomposing action on the already added soluble saltof sulfur, such for example, as acetic, trichloracetic sulfuric,hydrochloric, hydrofluoric, or admixtures thereof. This dilute aqueoussolution of acid may be prepared to any required extent of dilution, butI usually make it in the ratio of one part of strong acid to about 50 ormore parts of water, and, if the solution be hot when being added to thelatex, the dilution may be as much as (or even more than) 100 parts ofwater to one part of acid, as heat enhances its decomposing action onthe soluble salt of sulfur, and its coagulating effect on the rubber. Ifdesired, the acid employed in the second or coagulating treatment of thelatex may also have creosote or carbolic acid dissolved in it beforebeing diluted down with water or the water used for diluting it may haveeither creosote or carbolic acid dissolved in it, as creosote issoluble. in water to the extent of one part in about 120 parts of water,and carbolic acid to the extent of one part in about '20 parts of water..Both of these substances have a coagulating action on the rubber whenin an acid condition. The quantity of the dilute aqueous solution ofacid to be added to the latex for this second, or coagulating treatment,should be only sufficient to cause coagulation and effectivedecomposition of the soluble saltor salts of sulfur used in the firsttreatment of the latex, and the consequent precipitation therefrom ofnascent sulfur. The rubber may now be removed from the mother liquor,and the remnants of the mother liquor which adhere to the rubber or arecontained in its cellular structure are washed out. This washing may bedone by passing the rubber through the ordinarily employed rubberwashing machines, or preferably by drawing or calendering it out intothin sheets or bands between rollers with water trickling over them,which water may, if, desired, be heated. The rubber at this stage,however. still has traces of the acid employed in the second treatmentof the latex, and as it is usually considered de sirable that the rubbershould be in as neutral a condition as possible before drying it, therolled out thin sheets or bands may now drated oxid of lime,

be passed through, immersed for a time, or washed in a water bathcontaining any substance or substances which will have a neutralizingeffect on the remnants of free acid in the rubber, for example analkaline substance such as a carbonate of soda, or hy-. or a carbonateof an alkaline earth (for instance, carbonate of magnesia), orprecipitated chalk, or oxid of zinc, or a sulfid or polysulfid of analkali may be used. The action of the neutralizing bath is enhanced ifit be heated. If desired, I may add chlorid of sodium to theneutralizing bath or washing water.

The rubber on being removed from the neutralizing bath may then befurther washed in-plain water to free it from any suitably adheringremnants of said neutralizingbath, so as to leave the rubber as far aspracticable in a neutral'condition. The rubber is now ready for drying,and may be pressed into thin cakes and dried in any of the ordinarilyemployed rubber drying apparatus, or, if finished in the form of thinsheets or bands, its drying can be easily efl'ected b hanging on polesin anairy room orshed: and, when sufficiently dried, it may be pressedin molds into blocks, or otherwise market.

Rubber thus prepared is in a thoroughly sterilized condition, and isfree or freer than customary from protein and such like impurities, andwhen dry it possesses elasticity and nerve to a very high degree. Italso has a more intimate and equal admixture of sulfur from the nascentprecipitation thereof throughout its mass, than can be obtained by themechanical admixture therewith of sulfur (usually flowers of sulfur) bythe ordinary process of mechanical maceration and kneading of same intothe raw rubber after it comes into the hands of the manufacturer;nevertheless, if before its manufacture into rubber goods andvulcanizing a further addition of sulfur be desirable, the manufacturercan incorporate same therewith in the usual way.

For either the first treatment of the latex with a soluble salt ofsulfur, or for the second treatment for coagulation of the rubber,

with acid as hereinbefore described, I do not limit myself to theparticular soluble salts of sulfur, oracids to which I have hereinreferred, as other salts of sulfur or other acids or acid substanceshaving similar or analogous effects may be used within the limits of theinvention, and without aflecting the generalprinciples thereof, as aboveset forth. a p

What I claim as my invention, and desire -to secure by Letters Patent,1s

1. A process of coagulating the rubber from the fluid latex, comprisingliberating prepared for transmission to the nascent sulfur in tion.

2. In the extraction orcoagulation of rubber from the latex, firsttreating the fluid latex with a soluble salt of sulfur as described, andsubsequently applying to the latex a reagent having a coagulating actionon the caoutchouc and a decomposing action on said soluble salt ofsulfur whereby sulfur is liberated in the coagulation substantially asand for the purposes set forth.

3. In the extraction or coagulation of rubber from the latex, firsttreating the fluid latex with a polysulfid of an alkali and subsequentlyapplying to the latex an acid substance, substantially as and for thepurposes set forth.

4. In a process for the treatment of rubthe latex during coagula- .berlatex, adding to the fluid latex asoluble 7. In a process for thetreatment of rubber latex, adding to the fluid latex a soluble salt ofsulfur capable of liberating nascent sulfur on treatment with an acidsubstance and also a disinfectant having no coagulating effect on thelatex when introduced thereinto, substantially as described.

' 8. In a process for the treatment of rubber latex, adding to the fluidlatex a soluble salt of sulfur capable of liberating nascent sulfur ontreatment with an acid substance, and a solution of an alkalizedphenoloid body, substantially as described.

9. In a process for the treatment of rubber latex, adding to the fluidlatex. asoluble salt of sulfur capable of liberating nascent sulfur ontreatment with an acid substance, and a solution of alkalizedcreocarbolic acid.

10. In a process for the treatment of rubber latex, adding to the fluidlatex a solut on of an alkali polysulfid and an alkalized phenoloid bodyin aqueous solution.

11. A process of extracting rubber from latex, comprising treating thefluid latex with a soluble salt of sulfur capable of liberating nascentsulfur on treatment with an acid substance for coagulating the rubberfrom the latex, adding an acid substance for coagulating the rubber andliberating nasa substance capable of neutralizing remnants of free acidin the rubber, substantially as described.

12. As a new product, a rubber impregnated with sulfur which has beenliberated therein as nascent precipitated sulfur during the coagulationof the rubber from the latex and is free or comparatively freefromprotein or like impurities.

13. A process for extracting rubber, comprising precipitating sulfur innascent condition together with a caoutchouc, from an alkalized latex;

14. A process for extracting rubber, comprising precipitating sulfur innascent condition together with a caoutchouc, from an alkalized latex,by means of an acid substance and of a sulfur compound capable ofreacting therewith to yield nascent sulfur.

In Witness whereof, I have hereunto signed my name in the presence oftWo subscribing witnesses.

SAMUEL CLELAND DAVIDSON.

Witnesses:

HUGH T. COULTER, JOHN JOHNSON.

